Audio amplifiers, such as class-D amplifiers may be used in various signal amplification circuits. The audio amplifier requires an input voltage that can be above the voltage of the battery powering the signal amplification circuit. For this reason, a boost circuit is provided for increasing the battery voltage above a certain reference voltage. The reference voltage may be constant or may vary dynamically to track the audio signal.
The boost circuit can be implemented as an inductive or a capacitive converter. Capacitive converters such as capacitive multipliers have a smaller size than inductive converters and for this reason are often preferred. However, current systems based on capacitive multipliers are sensitive to variations in the battery voltage. For instance, if the audio signal increases, the audio amplifier may require more power and deplete the battery. Such changes in battery voltage lead to significant variations in the voltage generated by the capacitive converter, which in turn reduces the quality of the audio signal.